Pneumatic control means for air blast circuit breaker



PNEUMATIC CONTROL MEANS FOR AIR BLAST CIRCUIT BREAKER Filed June 18, 1965 5 Sheets-Sheet 1 //v vE/vram 0MoA/0 TIME/5S la/Tomi; 50M

Oct. 11, 1966 E.THURIE$ ETAL 3,278,711

PNEUMATIC CONTROL MEANS FOR AIR BLAST CIRCUIT BREAKER Filed June 18, 1966 s Sheets-Sheet z BY g 11, 1 E. THURIES ETAL 3,

PNEUMATIC CONTROL MEANS FOR AIR BLAST CIRCUIT BREAKER Filed June 18, 1963 5 Sheets-Sheet 3 United States Patent 3,278,711 PNEUMATIC CONTROL MEANS FOR AIR BLAST CIRCUIT BREAKER Edmond Thuries and Antoine Bon, Villeurbanne, France,

assignors to Compagnie Generale dElectricite, Paris,

France Filed June 18, 1963, Ser. No. 288,637 Claims priority, application France, July 2, 1962, 902,684 8 Claims. (Cl. 200-148) Pneumatic high-voltage circuit breakers generally comprise a plurality of breaking chambers in series, the number of which varies with the voltage of the supply system and the breaking power of the apparatus. These chambers are often shunted by capacitances to distribute the voltage and by resistances to facilitate certain breaking actions or to reduce the overvoltages. In order to reduce the time required to eliminate faults and in order to increase the effectiveness of the blowing action by reducing the dead volumes and the losses of pressure, these breaking chambers are gen-rally continously maintained under pressure, when in the inoperative position, by means of sealing devices which are frequently downstream of the breaking contacts in the air blast circuits. In apparatus of this type, it is desirable to minimize the diameter of the insulating jackets of the breaking chainbers, because the difficulty in manufacturing these parts and their cost increase very rapidly with the diameter, especially when they are made of ceramic materials. In addition, the rate of flow of the air blast and therefore the diameter of the nozzle tubes, must be increased in order to ensure a high breaking power. The means according to the invention make it possible more especially to obtain a high value of the ratio between the diameter of the air blast nozzle tubes and the internal diameter of the insulating jacket.

The present invention relates to a pneumatic circuit breaker of the type comprising at least one breaking chamber disposed within an insulating jacket, the latter being maintained under permanent pressure by means of air blast valves situated downstream of the discharge path of the gases, characterized by the fact that the element for blowing and extinguishing the arc constitutes a member extending axially from one end of the insulating jacket to the other, the said element being provided at each end with a valve, which is closed when the circuit breaker is in the closed position, and being connected to the atmosphere, at the instant of the tripping, by automatic opening of one of the valves, the pressure drop thus produced the element being transmitted through the latter to the second valve in order to open it, and the compressed air contained in the insulating jacket outside the said element then producing in the central portion of the element, after separation of the movable contact, the double blowing of the arc towards the atmosphere by way of the two ends of the breaking chamber.

A preferred embodiment will hereinafter be described by way of illustration and without in any way limiting the invention, with reference to the accompanying drawings.

FIGURE 1 is a longitudinal sectional view of a breaking chamber according to the invention, the electrical contacts being in closed positions;

FIGURE 2 is a magnified view of the electrical contacts of FIGURE 1, the contacts being shown in open position;

FIGURE 3 is a transverse sectional view of the fixed contacts, taken along line II of FIGURE 2;

FIGURE 4 is a transverse sectional view of the fingers of the fixed contacts taken along line II-II of FIGURE 2; and

3,278,711 Patented Oct. 11, 1966 FIGURE 5 is a transverse sectional view of the sliding contacts taken along line IIIIII of FIGURE 2.

The breaking chamber of FIGURE 1 is conventionally supported by an insulating column (not shown), which serves at the same time as a protective envelope for the supply duct 1 through which compressed air is fed to the chamber and, in accordance with the illustrated construction, for the control ducts 2 and 3 giving respectively the closing and opening orders, or, in the case of mechanical control for insulating linkages mechanically controlling the opening and closing valves.

The electric circuit of the circuit breaker in accordance with the invention comprises the metal member 4 connected to an input terminal (not illustrated), a tube 37, a sliding contact diagrammatically indicated at 5, a contact tube 7 driven by a piston 8, and the main contact dogs 9 and 59 protected by a casing 10 and supported by a metal member 11 connected to an output terminal (not shown). The arcing chamber is protected from weather influences by an insulating jacket 12.

The upper face 13 of the piston 8 communicates through a duct 14 with a closing valve 15 driven by a piston 16, which is biased in the illustrated position by action of a spring 17 and is provided with an orifice.18 which produces a static balancing of the pressures on the two faces of the piston after a predetermined time, which is a function of the cross-section of the orifice. The valve 15 connects the duct 14 either to the supply duct 19 connected to the pipe 1 under pressure, or to the outlet orifice 20 for discharge into the atmosphere.

The lower face 21 of the piston 8 communicates through the duct 22, the time delay member 23 and the duct 24 with the opening valve 25, which is driven by the piston 26 biased by a spring 27. Like piston 16, the piston 26 is formed with an orifice 28 for the static balancing of the pressures on the two faces thereof. Through ducts 29 and 30, the valve 25 connects the lower face 31 of the air blast valve 32 either to the compressed-air supply via the duct 33 connected to the pressure pipe 1, or to the outlet orifice 34 for discharge into the atmosphere. The air blast valve '32 biased by the spring 35 moves under the action of the pressure existing in the space 36 communicating with the supply pipe 1.

The interior of the tubes 37 and 38, of which the ends 39 and 40 may, if desired, be profiled to form air blast nozzles, communicate through the ducts 41 and 42 with the lower face 43 of the air blast valve 44 returned, which is biased by the spring 45. The other face of air blast valve 44 is subjected to the pressure existing in the space 46 communicating with the duct 47 leading into the interior of the insulating jacket 12, which is in turn supplied with air pressure via line 1.

When the air blast valves 32 and 44 are in the closed position, and thus compress the springs 35 and 45, during the breaking of the arc, the blowing air passes through the chambers 48 and 49, the latter of which is in communication with the space 50. Before discharge into the atmosphere, the arc gases are cooled in the flame arresters 51 and 52. At the end of the opening of the switch, the reclosing of the air blast valves 32 and 44 under the action of the springs 35 and 45 is automatically brought about by the time-delay slide valves 53 and 54 in a manner to be described more fully.

When at rest in the open or closed position, the whole of the chamber is normally under compressed-air pressure via pressure line 1.

The apparatus operates as follows:

The closing of the breaking chamber is obtained either by the mechanical control of the valve 15 or, as in the construction of FIGURE 1, by an introduction of pressure in the pipe 2 which serves to shift the piston 16 against the bias of spring 17. The resulting displacement of the valve 15 closes the duct pressure 19 and produces a pressure reduction on the upper face 13 of the piston 8 by placing the duct 14 in communication with the outlet orifice 20 connected to the atmosphere. The upward displacement of the piston 8 due to pressure applied to the piston via duct 22 brings the tube 7 into con- ,tact with the dogs 9 and 59. Immediately after the closing of the contact the application of pressure to control duct 2 corresponding to the making order is automatically cancelled in the control system with the aid of a time-delay slide valve (not shown), whereby immediate opening in the event of closure on short-circuit is rendered possible. The orifice 18 of the piston 16 by which the space containing the spring 17 is filled then enables the spring 17, with the desired time lag, to reclose automatically the valve 15 when equilibrium is substantially reached between the pressures on the two faces ofthe piston 16. The piston 8, of which the two faces 13 and 21 undergo equal pressures, remains at rest in the closed position.

The breaking chamber is opened either by the mechanical control of the valve 25 or, in accordance with the construction shown in the figure, by an introduction of pressure in the pipe 3 acting on the piston 28. The displacement of the valve 25 closes the duct 33 under pressure and produces a pressure reduction in the ducts 24 and 30 by connecting them to the orifice 34 communicating with the atmosphere. The operations succeed one another in the following order:

The pressure reduction in the ducts 29 and 30 and on the face 31 of the air blast valve 32 causes opening of the latter under the action of the pressure existing in the space 36. The interior of the tubes 37 and 38 therefore comes into communication with the. space 48 connected with the atmosphere by the flame arresters 51. This connection to the atmosphere is rendered possible by the contact tube 7, which effects an isolation between the interior of the tubes 37 and 38 and the remainder of the volume contained in the insulating jacket 12. Having regard to the great rapidity of the effects, sufficient fluid tightness is ensured. The pressure reduction in the tubes 37 and 38 is transmitted to the face 43 of the air blast valve 44 through the ducts 41 and 42. The valve opens under the action of the pressure existing in the space 46.

The pressure reduction in the duct 24 is transmitted to the face 21 of the piston 8 through the duct 22, but with some delay determined by the time delay member 23, which permits displacement of the piston 8 only when the valves 32 and 44 have been opened. This arrangement ensures vigorous blowing of the are as soon as it is formed between the dogs 9 and 59 and the movable contact tube 7. The pressure existing in the insulating jacket 12 produces a double blowing towards the atmosphere through the tubes 37 and 38, the spaces 48 and 49 and the flame arrestors 51 and 52 respectively. The seats of the arc, which are driven by the glowing, first shift along the ends 39 and 40 of the tubes 37 and 38 and then within the interior of the tubes 37 and 38 themselves. The arc is extinguished at a passage of the current cycle through zero succeeding the separation of the contacts, in such manner that the mean breaking time is generally less than a half-cycle of the current wave.

After the extinction of the arc, the valves 32 and 44 automatically close again under the action of the time delay slide valves 53 and 54. The movements to the right of the valve 53 and 54 close the ducts 30 and 41 by which the faces 31 and 43 of the air blast valves 32 and 44 were placed in communication with the atmosphere, and connect these faces to the pipe 1 under pressure through the ducts 29 and 72 on the one hand, and 42, 73 and 47 on the other hand.

During these operations, the space containing the spring 27 has been filled through the orifice .28 in the piston 26, and the cross-section of the said orifice is such that the spring 27 automatically commences the re-closing of the opening valve 25 (when equilibrium between the pressures on the two faces of the piston 26 is substantially reached) only after the reclosing of the valves 32 and 44.

The means illustrated in FIGURE 1 have the following features and advantages:

The movable tubular contact is concentric with and outside the two air blast tubes by which the arc gases are discharged and its slides on the said tubes with small clearance. This arrangement simultaneously makes it possible to discharge, before the break, the compressed air in the volume situated downstream of the main contacts in the discharge path of the gases, and to bring this volume to a pressure fairly close to atmospheric pressure (whereby the effectiveness of the blowing at the separation of the contacts is increased) and to obtain automatic operation of the valve 44 which is further from the opening valve 25, by using for this purpose the metal blowing tubes 37 and 38 necessary for the breaking, but without involving the use of any additional insulating duct in parallel with the insulating jacket 12 of the breaking chamber.

The opening and closing, which are controlled by two separate pneumatic control pulses or by two separate mechanical transmissions, avoid reclosing of the contacts in .and 38 (which dimensions mainly determine the breaking power), to give the insulating jacket 12 the minimum internal diameter. The apparatus always utilizes the control by pressure reduction for the two air blast valves and for the movable contact piston. The use of alternate temporary pressure drops for controlling the latter makes it possible to limit the movable packings to only one per operating order.

The air blast valves 32 and 44 are situated immediately at the outlet of the air blast tubes 37 and 38 without any change in the cross-section or in direction. This arrangement, which avoids pressure losses, makes it possible to obtain high performances at break and to construct the seals and the pistons of the valves themselves with smaller dimensions.

The maintenance under permanent pressure of the assembly comprising the chamber of the control system and the transmission ensures good dielectric strength, avoids condensation and reduces the danger of corrosion of the accessories (valves, valve members, etc).

The performance of the functions of the electric contacts and of the gas discharge tubes by means of separate members renders possible a better protection of the contacts from destruction due to the arc and enables the inlets 39 and 40 of the discharge tubes, on which the arc becomes seated during a part of the breaking period, to be made of materials having very high arcing resistance. The use of multiple contact dogs ensures a high closing power.

The automatic time-delayed reclosing of the control and air blast valves renders possible the performance of precise and short operating cycles. At the same time, this arrangement renders possible high breaking performance owing to the large diameters of the nozzle tubes, and low consumption of air owing to the reduced duration of the blowing, which is then only slightly greater than the duration of the arc.

The mechanical control of the valves 15 and 25 makes it possible to minimize the operating times and their pneumatic control generally leads to the simplest and most economical constructions.

The sliding contact as illustrated in FIGURE 2 has very small dimensions and ensures electrical connection between the two fixed concentric conductive tubes which are electrically connected to the input and output terminal connecting members of the circuit breaker. The said sliding contact consists of resilient folded conductive tapes comprising a large number of folds and affording multiple contact points between the tapes and each of the conductive tubes. The pressure may with advantage be provided by some degree of compression of the tape or tapes after they have been positioned between the tubes.

In accordance with another feature of the invention, the tape or tapes are made of trimetal material.

Preferably, the two outer faces of the tape or tapes consist of metals having very low contact resistance, while the central strip of the tape or tapes is resilient and consists of a copper-chromium alloy having a high copper content.

The contact and breaking member comprises two fixed hollow tubes 6 and 55 electrically connected to the input and output terminal connecting members of the circuit breaker, as previously described. The distance between the ends 39 and 40 of the tubes 55 and 6 defines the insulating distance when the said circuit breaker is in the open position. A movable cylindrical conductive portion 7, coaxial with the tubes 6 and 55 and external thereof, forms an integral part with the piston 8 by which the movable portion 7 is driven. The electric connections between the movable portion 7 and the terminal connecting members of the circuit breaker are made on the one hand with the terminal connecting member connected to the tube 55 by means of the sliding contact 5, and on the other hand, with the terminal connecting member connected to the tube 6 by means of the make and break contact 59.

The sliding contact 5 comprises one or more resilient conductive tapes folded in concertina fashion, such as 56, 57, 58 These tapes are folded with a fairly small pitch, lapped around a circumference between the tube 55 and the movable portion 7 as shown in FIGURE 5, and fitted into slots either in the movable portion 7 as shown in FIGURE 2, or in a variant, in the fixed member 55.

Each fold of the tapes 5 thus connects the outside surface of the member 55 to the inside surface of the memher 7 along short paths consisting of a metal of good conductivity. The flow of the current between the members 55 and 7 is thus divided into a large number of current streams due to the large number of folds. For a given cross-section of the resilient conductive tape 5 and for boundary current densities, the steady current and the short-circuit current undergone during a short time are substantially proportional to the number of current paths and can thus be very high.

The large number of contact points distributed around the entire external periphery of the member 55 and the entire internal periphery of the member 7 makes it possible to withstand a high peak value of the short-circuit current, since the latter is substantially proportional to the number of contact points, While adopting a low unit pressure of the tapes on the members 55 and 7. This low unit pressure reduces the friction and the wear on the surfaces.

In order to obtain simultaneously low contact resistances which are unaffected by oxidation between the members 55 and 7 and the tapes 5, a low ohmic resistance of the tapes themselves and a good preservation in time of the resilience of the tapes despite the heating of the contacts, there may with advantage be employed for the folds 56, 57, 58 tapes of trimetal materials. The two external faces of the tape consist of metals having very low contact resistance and low sensitivity to oxidation, such as fine silver, for example, and the central strip of a material which is a fairly good conductor and retains its resilience at the temperatures reached when a short-circuit succeeds a state of continuous operation. For this purpose, copper alloys having a high copper content may be employed, such as the chromium-containing copper employed in preference to rolled copper and to phosphor bronze.

This type of contact withstands high currents in continuous operation and in short-circuit with low overall U dimensions, metal weight and friction. Its low heating under high currents makes it possible to avoid increasing the diameters of the contact tubes. It is also very economical, because it can be rapidly installed with simple tooling, formed of a detachable inlet cone, without any necessity for drilling, brazing or screwing.

The make and break contact is obtained by penetration of the movable portion 55 under a ring of contact dogs comprising massive studs such as 9 and 59 connected to the fixed tube 6 and to the corresponding terminal connecting member by resilient conductive strips such as 60 and 61. One or more dogs such as 9 extend beyond the dogs such as 59 and form arcing contacts. Springs working in compression, such as 62 and 63, directly apply to the contact point of each dog the force necessary to permit the passage of the steady current and of the short-circuit current without dangerous heating, to withstand the peak value of the closing current without pitting and to avoid rebounding during the contactmaking at closing. The springs such as 62 and 63 bear on a ring 64 concentric with the tube 6.

The contact dogs 9 and 59 rest on the movable portion 7, as illustrated in FIGURE 1 in the closed position, and also rests on the annulus 65 fixed on the tube 6 and forming an internal abutment in the open position.

The ring 64 formed with apertures such as 66, the annulus 65 formed with orifices such as 77 and the combination of contact dogs are so disposed that the blowing fluid flows freely around these members at the opening.

The arr-angemment adopted thus makes it possible to protect the whole of the contact 6 against deterioration due to the are at opening owing to the effective sweeping of the air current. At the opening, the gas discharge valves (not shown) situated at the ends of the tubes 6 and 55 are opened. The separation of the contacts takes place between the end 67 of the movable portion 7 and the arcing contact dog or dogs 9, which thus protect the other permanent contact dogs 59 from the action of the arc. The arc struck between the ends 67 and 9 is carried along by the compressed fluid contained in the insulating jacket 12, which fluid travels towards the interior of the tubes 6 and 55. The are is then struck between the end 67 and the end 40 of the tube 6, and then, when the movable portion 7 has completed a sufficient travel, it is struck successively between the ends 40 and 39 of the tubes 6 and 55 and after its seats have entered the said tubes, in some cases between the electrodes 68 and 69 which are generally, but not necessarily, provided inside the tubes 55 and 6, and which are intended to limit the length of the arc in order to facilitate its breaking. While at breaking the arc is directed towards the interior of the tubes 6 and 55 by the quenching fluid, in the closed position, the current passes through the contact 6 and the outside of the movable tubular contact 7.

Finally, the closing operation is performed by the contact-making of the end 67 of the movable portion 7 with the arcing contact dogs 9, which protect the permanent contact dogs 59 by virtue of their advanced position.

There will therefore simultaneously be obtained a low contact resistance and thus low heating in the closed position, and good protectionv against deterioration due to the are both at making and at breaking by covering the external surface of the movable portion 7 and the contact studs of the dogs 59 with a material which is a very good conductor, preferable silver, and by making the end 67 and the inside surface 70 of the movable portion 7, the ends 39 and 40 of the air blast tubes 55 and 6 and the studs of the arcing contact dogs 9 of a material which is resistant to arcing, such as tungsten alloys, or by covering them with such a material.

In the closed position, the fixed contact 6 and the movable portion 7 are set back in relation to the ends 39 and 40 of the fixed air blast tubes 55 and 6, which thus determine the opening distance.

Of course, the embodiment described purely by way of tact member including opening means for effecting illustration may be varied and modified in a number of reciprocation thereof to said second closed position ways without departing from the scope of the present and means for controlling the opening of said air ber,

means for ensuring an electrical contact between said movable member and said second fixed member upon engagement thereof,

means for controlling the position of said movable coni ti blast valves upon disengagement of said movable con- W l i tact member from said second fixed member, the 1. Electrical circuit breaker arcing chamber comprising air under pressure contained in said housing means a soul-Ce f i under re, producing the blowing of the electrical arc through housing means continuously connected to said source both said first and second fixed members upon openof air under pressure including an electrically ining of said air blast valves, sulating lateral wall, 10 said movable contact member being mounted slidably first and second fixed hollow cylindrical contact memalong the outer surface of said first fixed member bers spaced opposite each other along a common so that in said first open position the tip of the movaxis within said housing means, said first and second able member is set back in relation to the end porfixed members extending through and being secured tion of said first fixed member facing said second to respective end walls of said housing means and fixed member, each having a blast valve for selectively connecting said means for ensuring the electrical contact between the space inside said fixed members with the atmossaid movable contact member and said second fixed phere in the open position thereof, and sealing said member comprising contact dogs contacting the tip space inside said fixed members from the atmosphere of said movable contact member upon engagement in the closed position thereof, thereof, said dogs including massive studs made of a removable hollow cylindrical contact member slidably material resistant to the electrical arc, said contact mounted on said first fixed member and operable to dogs being secured to the outer surface of said second reciprocate from a first open position to a second fixed member, closed position in engagement with an end portion the outer surface of said second fixed member comof said second fixed member, prising fixed retaining and abutment members comeans for ensuring a continuous electrical contact beoperating with the tip of said movable contact memtween said movable member and said first fixed member in its engaged position, said retaining and abutb ment members having aperture means for facilitating means for ensuring an electrical contact between said the blowing of the are at the separation of the movmovable member and said second fixed member upon able contact member from said second fixed member. engagement thereof, 3. Electrical circuit breaker arcing chamber comprising means for controlling the position of said movable cona source of air under pressure,

tact member including opening means for effecting housing means continuously connected to said source reciprocation thereof to said second closed position of air under pressure including an electrically inand means for controlling the opening of said air sulating lateral wall, a blast valves upon disengagement of said movable first and second fixed hollow cylindrical contact memcontact member from said second fixed member, the bers spaced opposite each other along a common air under pressure contained in said housing means axis within said housing means, said first and second producing the blowing of the electrical are through fixed members extending through and being secured both said first and second fixed members upon open- 40 to respective end walls of said housing means and ing of said air blast valves, each having a blast valve for selectively connecting the dimensions of the inner surface of the movable com the space inside said fixed members with the atmostact member corresponding to the outer portion of phere in the open position thereof, said second fixed member so that upon movement a removable hollow cylindrical contact member slidably of the movable contact to encompass a certain length mounted on said first fixed member and operable to of said second fixed contact, an air tightness of short reciprocate from a first open position to a second duration as compared to that provided by said blast closed position in engagement with an end portion valves is provided between the inner space defined of said second fixed member, by said housing means and the inner space defined means for ensuring a continuous electrical contact beby said movable contacts and said fixed members. 5 tween said movable member and said first fixed mem 2. Electrical circuit breaker arcing chamber comprising ber, a source of air under pressure, means for ensuring an electrical contact between said housing means continuously connected to said source movable member and said second fixed member upon of air under pressure including an electrically inengagement thereof, sulating lateral wall, means for controlling the position of said movable confirst and second fixed hollow cylindrical contact merntact member including opening means for effecting bers spaced opposite each other along a common reciprocation thereof to said second closed position axis within said housing means, said first and second and means for controlling the opening of said air fixed members extending through and being secured blast valves upon disengagement of said movable conto respective end walls of said housing means and tact member from said second fixed member, the air each having a blast valve for selectively connecting und r pressure Contained in said housing means prothe space inside said fixed members with the atmosducing the blowing of the electrical arc through both phere in the open position thereof, said first and second fixed members upon opening a removable hollow cylindrical contact member slidof said air blast valves,

bl mounted on id fi t fi d member d operasaid means for ensuring a continuous electrical contact. ble to reciprocate from a first open position to a between said movable member and said first fixed Second l d position i engagement with an end member being a sliding contact comprising a resilient portion of said second fixed member, tape having zig-zag like folds disposed around said means for ensuring a continuous electrical contact befirst fix d member in Such a manner that the contact tween said movable member and aid first fixed mem- Of the resilient tape With the removable member and said second fixed member is carried out along radial segments defined by said folds. 4. Electrical circuit breaker arcing chamber according to claim 3 wherein said resilient tape is made of a trimetal material having a central layer made of a metal having 9 a high resilience at high temperature and a high electrical conductivity and two external layers made of at least one metal having a very low contact resistance and low sensitivity to oxidation.

5. Electrical circuit breaker arcing chamber according to claim 4 wherein said metal having a high resilience is a copper chromium alloy having a high copper content, said one metal having a very low contact resistance being silver.

6. Electrical circuit breaker arcing chamber comprising a source of air under pressure,

housing means continuously connected to said source of air under pressure including an electrically insulating lateral wall,

first and second fixed hollow cylindrical contact members spaced opposite each other along a common axis within said housing means, said first and second fixed members extending through and being secured to respective end walls of said housing means and each having a blast valve for selectively connecting the space inside said fixed members with the atmosphere in the open position thereof,

a removable hollow cylindrical contact member slidably mounted on said first fixed member and operable to reciprocate from a first open position to a second closed position in engagement with an end portion of said second fixed member,

means for ensuring a continuous electrical contact between said movable member and said first fixed member,

means for ensuring an electrical contact between said movable member and said second fixed member upon engagement thereof,

means for controlling the position of said movable contact member including opening means for effecting reciprocation thereof to said second closed position and means for controlling the opening of said air blast valves upon disengagement of said movable contact member from said second fixed member, the air under pressure contained in said housing means producing the blowing of the electrical arc through both said first and second fixed members upon opening of said air blast valves,

first pressure means responsive to said source of air under pressure for holding said first air blast valve in closed position,

control valve means for selectively connecting said first pressure air blast means with the atmosphere, where- 10 by said air blast valve is opened and the pressure is reduced in the space enclosed by said movable and fixed members, second pressure means responsive to said source of air 5 under pressure for holding said second airblast valve in closed position and conduit means for connecting said second pressure means with the space enclosed by said movable and fixed members, a reduction in the pressure in said space causing the simultaneous opening of said second air blast valve,

said means for controlling the position of said movable contact including a piston connected With said movable contact member, and located within a cylinder having a chamber, normally under pressure, connected with said control valve means through pressure delay means, said chamber being selectively connected with the atmosphere by said control valve means after the opening of said first and said second air blast valves, whereby the movable contact member is disengaged from said second fixed member.

7. Electrical circuit breaker arcing chamber according to claim 6 wherein said control valve means and said conduit means respectively include a time delay slide valve means operable to restablish a high pressure in said 25 first and second pressure means a determinable time after the electrical arc is extinguished, whereby said first and second air blast valves are closed.

8. Electrical circuit breaker arcing chamber according to claim 7 wherein said control valve means comprises 30 delayed return means operable to replace said control valve means to its initial state after the closing of said first and second air blast valves.

References Cited by the Examiner ROBERT K. SCHAEFER, Primary Examiner.

KATHLEEN H. CLAFFY, ROBERT S. MACON,

Examiners. P. E. CRAWFORD, Assistant Examiner. 

1. ELECTRICAL CIRCUIT BREAKER ARCING CHAMBER COMPRISING A SOURCE OF AIR UNDER PRESSURE, HOUSING MEANS CONTINUOUSLY CONNECTED TO SAID SOURCE OF AIR UNDER PRESSURE INCLUDING AN ELECTRICALLY INSULATING LATERAL WALL, FIRST AND SECOND FIXED HOLLOW CYLINDRICAL CONTACT MEMBERS SPACED OPPOSITED EACH OTHER ALONG A COMMON AXIS WITHIN SAID HOUSING MEANS, SAID FIRST AND SECOND FIXED MEMBERS EXTENDING THROUGH AND BEING SECURED TO RESPECTIVE END WALLS OF SAID HOUSING MEANS AND EACH HAVING A BLAST VALVE FOR SELECTIVELY CONNECTING THE SPACE INSIDE SAID FIXED MEMBERS WITH THE ATMOSPHERE IN THE OPEN POSITION THEREOF, AND SEALING SAID SPACE INSIDE SAID FIXED MEMBERS FROM THE ATMOSPHERE IN THE CLOSED POSITION THEREOF, A REMOVABLE HOLLOW CYLINDRICAL CONTACT MEMBER SLIDABLY MOUNTED ON SAID FIRST FIXED MEMBER AND OPERABLE TO RECIPROCATE FROM A FIRST OPEN POSITION TO A SECOND CLOSED POSITION IN ENGAGEMENT WITH AN END PORTION OF SAID SECOND FIXED MEMBER, MEANS FOR ENSURING A CONTINUOUS ELECTRICAL CONTACT BETWEEN SAID MOVABLE MEMBER AND SAID FIRST FIXED MEMBER, MEANS FOR ENSURING AN ELECTRICAL BETWEEN SAID MOVABLE MEMBER AND SAID SECOND FIXED MEMBER UPON ENGAGEMENT THEREOF, MEANS FOR CONTROLLING THE POSITION OF SAID MOVABLE CONTACT MEMBER INCLUDING OPENING MEANS FOR EFFECTING RECIPROCATION THEREOF TO SAID SECOND CLOSED POSITION AND MEANS FOR CONTROLLING THE OPENNG OF SAID AIR 